In one method of manufacturing electrical terminals, the terminals are stamped and formed from metal strip and are attached to a carrier strip. This carrier strip is useful for strip feeding the terminals through successive manufacturing operations. One necessary manufacturing operation involves plating, i.e., electroplating the electrical contact surfaces of the noble metal alloys. These metals are characterized by good electrical conductivity and little or no formation of oxides that reduce the conductivity. Therefore, these metals, when applied as plating, will enhance conductivity of the terminals. The high cost of these metals has necessitated precision deposition on the contact surfaces of the terminals, and not on surfaces of the terminals on which plating is unnecessary.
Apparatus for plating is called a plating cell and includes an electrical anode, an electrical cathode comprised of the strip fed terminals, and a plating solution, i.e., an electrolyte of metal ions. A strip feeding means feeds the strip to a strip guide. The strip guide guides the terminals through a plating zone while the terminals are being plated. The plating solution is fluidic and is placed in contact with the anode and the terminals. The apparatus operates by passing electrical current from the anode through the plating solution to the terminals. The metal ions deposit as metal plating on those terminal surfaces in contact with the plating solution.
There are disclosed in U.S. Pat. Nos. 4,384,926, 4,427,498 and 4,555,321, owned by this Assignee, plating apparatuses as in which the interior surfaces of strip fed terminals can be plated by supplying plating fluid through nozzles and over associated anode extensions that are mounted for reciprocation into and out of the interiors of terminals. In the first two patents, the anode extensions are mounted within their associated nozzles. In the third patent, the anode extensions are mounted separately and apart from the nozzles and enter the terminals from a different direction than that of the plating fluid.
The apparatuses disclosed in the three referenced patents are designed to be used with stamped and formed terminals, wherein the contact zone is located inside the formed terminal. Each apparatus is comprised of an assembly of conductive and dielectric parts, all mounted for rotation on a stationary axis. Each of the apparatuses consists generally of a mandrel that is continuously rotated as strip fed electrical terminals are continuously fed to the mandrel, partially wrapped against it and exited from it. The mandrel is turreted with a plurality of nozzles distributed about its axis of rotation. Anodes are associated with the nozzles and are mounted for movement into and out of the interiors of the terminals that are against the mandrel. A conduit supplies plating solution under pressure through the nozzles and upon the anodes. The nozzles inject plating solution into the interiors of the terminals in which the anodes are received. A source of electrical potential supplies an electrical current flow from the anodes, through the plating solution and into the interiors of the terminals in which the anodes are received. In essence, each mandrel has a plurality of plating cells distributed about its axis of rotation.
Anode members or anode extensions are mounted within the assembly such that they can be moved into and out of the contact zone inside a formed terminal. The conductive anode members are either continually in mechanical engagement and electrical contact with or brought into electrical contact with an electrically charged member just prior to moving the anode member inside the terminal to selectively plate the contact zone. Generally the anode members are held against the charged member under tension by using either a spring in the anode extension member itself or by spring loading the anode extension members against a conductive plate of the apparatus or both. The anode members are then moved into and out of aligned terminal members by hydraulic, mechanical or a combination of means.
When plating electrical terminals in such an apparatus, it is important that an essentially uniform current be maintained in each of the individual plating cells which are distributed around the apparatus. The continual flexing movement of the spring portions owing to repeatedly engaging and disengaging terminals, friction between moving parts and exposure to corrosive chemicals can gradually affect the mechanical engagement between the anode member and the anode plate such that the current level within the cells is no longer uniform because one or more of the anode members are not functioning as intended. It is desirable, therefore, to provide an assured electrical interconnection that is not affected by mechanical factors such as those described above.
To achieve plating deposit in the desired area, it is also important that the anode members are moved into complete engagement with the associated terminal. In addition it is important that the anode members be removed completely from the terminal to prevent damage to either the anode member, the terminal or both as the terminal exits the apparatus. It is desirable, therefore, to provide a positive means to assure proper movement of the anode members.